Global varus malalignment increase from double-leg to single-leg stance due to intra-articular changes
Abstrakt
Purpose Preoperatively planned correction for tibial osteotomy surgery is usually based on weightbearing long-leg Xrays, while the surgery is performed in a supine non-weightbearing position. The purpose of this study was to assess the differences in lower limb alignment in three different weightbearing conditions: supine position, double-leg (DL) stance and single-sleg (SL) stance prior to performing a medial opening wedge high tibial osteotomy (MOWHTO) for varus malalignment.
The hypothesis of this study was that progressive limb-loading would lead to an increased preoperative varus deformity. Material and methods This retrospective study included 89 patients (96 knees) with isolated medial knee osteoarthritis (Ahlback grade I or II) and significant metaphyseal tibial vara (> 6 degrees).
The differences between supine position, DL stance and SL stance were analysed for the hip-knee-ankle angle (HKA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), weight-bearing line ratio (WBL) and joint line convergence angle (JLCA). Results From a supine position to DL stance, the HKA angle slightly increased from 175.5 degrees +/- 1.1 degrees to 176.3 degrees +/- 1.1 degrees and JLCA changed from 2.0 degrees +/- 0.3 degrees to 1.8 degrees +/- 0.3 degrees without a statistically significant difference.
From DL to SL stances, the HKA angle decreased from 176.3 degrees +/- 1.1 degrees to 174.4 degrees +/- 1.1 degrees (p < 0.05) and the JLCA increased from 1.8 degrees +/- 0.3 degrees to 2.6 degrees +/- 0.3 degrees (p < 0.05). A significant correlation was found between Delta HKA and Delta JLCA between the DL and the SL stances (R-2 = 0.46; p = 0.01).
Conclusion Varus malalignment increases with weight-bearing loading from double-leg to single-leg stances with an associated JLCA increase. Thus, single-leg stance radiographs may be useful to correct preoperative planning considering patient-specific changes in JLCA.
Level of clinical evidence III, retrospective comparative study.